In the case of utilization of light, such as sunlight, whose angle of incidence gradually changes, in order to attain an effective utilization, a light source tracking device which is so controlled as to point to the direction of incident light is needed.
When a light input or reception means is always maintained to point to the direction of incidence of light by the light source tracking device, the incident light can be received in a most effective manner. However, as the angle of incidence of, for example, sunlight gradually changes according to the season of the year and from the sunrise to the sunset, an effective light source tracking device must necessarily be complicated in construction and expensive and cannot be used practically.
The present invention has been made to overcome the above and other problems encountered in the prior art and has for its object to provide a device for changing the directions of light rays, which is maintained stationary in the case of receiving light rays whose angles of incidence varies from time to time or light rays from any directions without the use of a light source tracking device and which can convert them into light rays within a predetermined direction range so as to facilitate the utilization of the received light rays.